1. Background of the Invention
This invention relates to self supporting carriers for routing flexible conduit.
2. Discussion of the Prior Art
Conduit carrier chains for guiding one or more cables, hoses or other flexible media (collectively referred to herein as conduits) from one location to a relatively movable location are well known. As applied to machine tools, the carrier is typically attached at one end to a stationary base or frame and at its other end to a mobile table or other member that moves back and forth in a relatively straight line.
Conduits are supported inside the carrier chain, which typically has a limited range of angular motion of one link relative to the next. This range may typically be from about 180.degree. to approximately 135.degree. or less. Between the base and the table, the chain extends from one end and supports itself in one relatively straight span along the line of motion, and curves at a certain radius to another relatively straight span that doubles back on the first span and extends to the other end of the carrier. As the table moves back and forth, the span lengths change as the chain follows the radius.
The precise limits of the range of link-to-link angular motion are chosen so that the chain is self supporting in the plane of motion defined by its two spans. In a typical installation, the chain is in a vertical plane, with at least its lower span substantially horizontal (the upper span may be inclined) and with the spans above one another. The chain is cantilevered out from its lower end along a lower span to the radius, which curves back on the lower span to define the upper span. The lower span supports the weight of the chain and all the conduits it carries for the entire length of the chain, which is determined by the length of the motion to be accommodated. The upper span supports the weight of itself and the conduits in the upper span. Such chains are therefore typically made with a certain unloaded concavity or "camber" upwardly so that when they are loaded with the cable and/or hoses and cantilevered from their lower ends, they are generally horizontal rather than sagging excessively from horizontal. Thus, the upper limit of the range of link-to-link angular motion may be somewhat less than 180.degree. to provide the camber, depending upon the length of motion to be accommodated and the weight of the carrier chain and conduits.
Cable carrier chains are also made for a certain radius, which determines the precise limit at the low end of the link-to-link angular motion. The minimum radius determines the distance that the two spans of the carrier are spaced apart, which may vary from application to application based upon space and end mounting considerations.
Since the length of motion, weight of conduits, end mounting, and available space can vary considerably from application to application, cable carriers have typically been specially engineered for each application. In addition to being relatively expensive and time consuming, it has been difficult in prior art carriers to adjust the camber and radius of carriers so as to fit particular applications. The difficulty of applying cable carriers to specific applications has also contributed to such carriers typically being sold as assemblies or completed installations. Consequently, a result has been inflexibility in adapting such carriers to other applications where they may otherwise be useful.